Hi - Good News for DDEC (I-II-II-IV) Owners with poor acceleration from a stop

In talking about 6V92TA's with a painfully slow response when starting from a dead stop only - seems their DDEC is set withsome kind of "smoke control" option - they do not smoke when you mash the throttle down

DDEC I - Thanks to the work of Butch Williams - Luke at US Coach stocks an EPROM replacement for approx $100 that will cure most N.J. MCI DDEC I of their poor acceleration. DDEC I's have a replaceable EPROMS and are not programable

DDEC II, DDEC III, DDEC IV,Bill Gerrie and I have worked on this problem for the last few days- Via long distance phone call Between Daytona and Toronto - Thankgoodness for "Unlimit USA/Canada phone plans)

<>The PROLINK was used to verify the correct action of Bill's TBS without the modifications

<>Bill came up with a unique solution - A 100 ohm resistor between pin B (sense line) and C (+5 volts) - will pull up the voltage at the sense line (pin B) to what would be an approx 4-5 psi boost voltage level (as measured/verified with the PROLINK)

<>The net result is that the DDEC thinks that there's is a little boost pressure available at IDLE and allows for more fuel to bedelivered to the injectors upon acceleration

<>This does mean that if you mash the pedal - you will produce some black smoke - adding a 100 ohm potentiometer to the existing100 ohm resistor will help you dial out excessive smoke - or - just use the throttle pedal wisely (especially in front of the smog control guys)

<>The PROLINK was used to verify the correct action of Bill's TBS without the modifications

<>Bill came up with a unique solution - A 100 ohm resistor between pin B (sense line) and C (+5 volts) - will pull up the voltage at the sense line (pin B) to what would be an approx 4-5 psi boost voltage level (as measured/verified with the PROLINK)

<>The net result is that the DDEC thinks that there's is a little boost pressure available at IDLE and allows for more fuel to bedelivered to the injectors upon acceleration

The DDEC guy at the DD truck shop at Stewart &Stevenson in Denver told me to put the 100 ohm resistor in series with the center wire from the boost sensor. To prevent problems at smog test, add a SPST switch in parallel with the resistor and close it when testing. I haven't tried it on my S-50 DDEC II engine yet. That engine is amazingly clean at smog test (275-HP version).

Ok, I must report. I have a roadburner. I installed the 100ohm resistor between the 5V line and the middle line of the turbos boost sensor plug. OMG, forgot i was in a bus. It really does make a huge difference. I had to be careful and not mash the accelerator(too much black smoke), but if you take care not to mash from a stop, the response is 100 times better than without the resistor. I cut some sheathing off the wires and twisted the resistor around each wire, then squeezed with pliers and put tight electricians tape over it. I should solder it, but the resistor ends are long enough to wrap 3 or 4 times easily, so the connection should be fine. I suggest others try it, thanks for the tip!!!!!!!!!!!!!!!!!!!!111

I picked up a potentiometer and some additional 150 and 220 ohm resistors yesterday. I'll try some additional testing this week. Per Greg Peterson, I am also wondering what the additional amperage is doing to the circuit. Has anyone run this way for an extended period of time? It would be nice to know someone has 200K miles on this mod and no problems:-)

I picked up a potentiometer and some additional 150 and 220 ohm resistors yesterday. I'll try some additional testing this week. Per Greg Peterson, I am also wondering what the additional amperage is doing to the circuit. Has anyone run this way for an extended period of time? It would be nice to know someone has 200K miles on this mod and no problems:-)

Logged

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

Actually the added resistor is in sort of a parrallel configuration - at worst case it could add 50 milliamp additional load to the 5v sensor supply line - thats 1/20 of an amp

you guys decide for ourselves -

Pete RTS/Daytona

Logged

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

The Turbo Boost Sensor is an unique IC Device (not just a simple variable resistor - I do not know it's actual internal configuration - the 100 ohm resistor appears to hold the bias at a level that approximates a few pounds of boost and seems to have no effect after the actual boost pressure climbs above that valve.

Update: I installed a 220ohm resistor in place of the 100 ohm and the slow acceleration was back. Now I did get my Pro-Link last week and while idling with the 100ohm resistor, I did not register any boost on the Pro-Link. Anyways, I installed the 100 ohm resistor back in place and road-burner is back.